What term describes the fragment ion that is passed through to the detector in tandem MS?

The term that describes the fragment ion that is passed through to the detector in tandem mass spectrometry (MS/MS) is the Product Ion, also commonly known as the Daughter Ion. In tandem MS, ions are first generated from a sample and then selected based on their mass-to-charge ratio. This selected ion undergoes further fragmentation in a collision chamber, resulting in smaller ions. These smaller ions, which are fragments of the original ion, are then analyzed and detected.

The reason why Product/Daughter Ion is the correct term is that it specifically refers to the ions that result from the fragmentation of the precursor ion. These daughter ions provide valuable structural information and help in identifying the original compound by analyzing their mass and abundance.

The other terms listed do not accurately describe this particular process. The term Fragment Ion is too general and does not specifically indicate that these ions are a product of a precursor ion's fragmentation. Selected Ion typically refers to the mass spectrometry process of isolating a specific ion rather than the fragmented ions produced. Finally, Mother Ion is not a standard term in mass spectrometry for describing these ions; instead, the precursor ion from which the daughter ions are derived is more appropriately called the Precursor Ion.